Band structure of ZrTe$_5$ measured by high-momentum-resolution photoemission spectroscopy

We have performed a systematic high-momentum-resolution photoemission study on ZrTe$_5$ using a photon energy of $6$ eV. We have measured the band structure near $\Gamma$, and quantified the gap between conduction and valence band as $25\pm5$ meV. We have also observed photon-energy-dependent spectral changes, and attributed these changes to final-state effects and the 3D nature of the material's band structure. Our observation suggests that ZrTe$_5$ is neither a 3D strong topological insulator, nor a Dirac semimetal. We further propose a model which promises to reconcile discrepancies on the existence of surface state in different literature studies of this material.